Strange NFS write performance Linux->Solaris-10/VXFS, maybe VW related
Subsystems (2)
----- Original Message ----
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From: Martin Knoblauch <[email protected]>
To: Chris Snook <[email protected]>
Cc: [email protected]; [email protected]; spam trap <[email protected]>
Sent: Saturday, December 29, 2007 12:11:08 PM
Subject: Re: Strange NFS write performance Linux->Solaris-10/VXFS, maybe VW related
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----- Original Message ----
Quoted 5 lines
From: Chris Snook
To: Martin Knoblauch
Cc: [email protected]; [email protected]
Sent: Friday, December 28, 2007 7:45:13 PM
Subject: Re: Strange NFS write performanceLinux->Solaris-10/VXFS,
maybe VW related
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Quoted 3 lines · Martin Knoblauch
Hi,
currently I am tracking down an "interesting" effect when writing
3) It sounds like the bottleneck is the vxfs filesystem. It only *appears* on the client side because writes up
until
dirty_ratio
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get buffered on the client.
If you can confirm that the server is actually writing stuff to
disk slower when the client is in writeback mode, then it's possible the Linux NFSclient is doing something inefficient inwriteback
mode.
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so, is the output of "iostat -d -l1 d111" during two runs. The first
run is with 750 MB, the second with 850MB.
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// 750MB
$ iostat -d -l 1 md111 2 md111 kps tps serv 22 0 14 0 0 0 0 0 13 29347 468 12 37040 593 17 30938 492 25 30421 491 25 41626 676 16 42913 703 14 39890 647 15 9009 141 7 8963 141 7 5143 81 7 34814 547 10 49323 775 12 28624 451 6 22 1 6 #### finish 0 0 0 0 0 0
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Here it seems that the disk is writing for 26-28 seconds with avg.
29
MB/sec. Fine.
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// 850MB
$ iostat -d -l 1 md111 2 md111 kps tps serv 0 0 0 11275 180 10 39874 635 14 37403 587 17 24341 392 30 25989 423 26 22464 375 30 21922 361 32 27924 450 26 21507 342 21 9217 153 15 9260 150 15 9544 155 15 9298 150 14 10118 162 11 15505 250 12 27513 448 14 26698 436 15 26144 431 15 25201 412 14 #### 38 seconds in run 0 0 0 0 0 0 579 17 12 0 0 0 0 0 0 0 0 0 0 0 0 518 9 16 485 8 6 9 1 7 514 9 7 0 0 0 0 0 0 541 9 8 532 10 6 0 0 0 0 0 0 650 12 7 0 0 0 242 8 9 1023 18 5 304 5 6 418 8 7 283 5 5 303 5 8 527 10 6 0 0 0 0 0 0 0 0 0 5 1 13 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 11 0 0 0 0 0 0 0 0 0 1 0 15 0 0 0 96 2 15 138 3 10 11057 175 6 17549 280 6 351 8 5 0 0 0 ##### 218 seconds in run, finish.So, for the first 38 seconds everything looks similar to the 750
MB case. For the next about 180 seconds most time nothing happens. Averaging 4.1 MB/sec.
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Maybe it is time to capture the traffic. What are the best tcpdump parameters for NFS? I always forget :-(
Cheers
Martin
Hi,
now that the seasonal festivities are over - Happy New Year btw. - any comments/suggestions on my problem?
Cheers
Martin